A89: Re: Re: Rotating Sprites

To: <assembly-89@lists.ticalc.org>
Subject: A89: Re: Re: Rotating Sprites
From: "B Clark" <nix249@mich.com>
Date: Wed, 7 Feb 2001 20:40:43 -0500
References: <000701c0914b$bed86000$93504f40@ees.eesc.com> <000401c0914d$f2439ac0$0c01a8c0@WinNATDomain>
Reply-To: assembly-89@lists.ticalc.org


Thanks, this is pretty much what I was looking for.

B Clark


> Hi!
>
> |     I have several ideas for some games, which require displaying a
sprite
> | at various angles. I remember something about using matrices to do this,
> but
> | I don't know how to implement this.  I'm looking for a C function which
> can
> | quickly rotate a sprite at various angles. Any ideas?
>
> Depending on what you want, yes.  If the angles are just 90°, 180°, and
> 270°, this is rather easy to do.  180° just involves switching rows in the
> sprite from the outside to the inside or verse vica.  90° and 270° are
more
> complicated:  You'll have to test each bit and put it in its new location.
> I don't want to think about any details right now, but the fact is that
it's
> doable.
>
> All other angles involve a lot of math, especially trigonometry.  For
small
> sprites, this also reduces quality a lot.  Calculating new positions for
all
> pixels is really slow as well.  I would recommend vectorizing your sprites
> into polygons and calculating the new points for all corners of the
> polygons.  Again, this involves trig; remember that floating point
functions
> are slow.  I don't want to go into any detail here; I assume you can do
the
> math.
>
> Sorry if I wasn't able to help a lot.
>
> Bye,
> Sebastian

References:

A89: Rotating Sprites

From: "B Clark" <nix249@mich.com>

A89: Re: Rotating Sprites

From: "Sebastian Reichelt" <SebastianR@gmx.de>